1. Field of the Invention
The present invention relates to an optical fiber which is a medium for transmitting high-energy beams within an ultraviolet range such as laser beams.
2. Description of the Prior Art
In the case where, by applying high-energy beams such as laser beams, such as medical uses where a diseased tissue is treated or in industrial uses where iron plates and the like are subjected to drilling, cutting and welding, an optical fiber has been used as a medium for transmitting high-energy beams. In order to transmit the energy of these high-energy beams efficiently, a low transmission loss is required for an optical fiber used for such a use. In addition, since the optical transmission loss changes in some conditions with time, it is desired that the optical fiber is superior in not only its initial characteristics but also in its characteristics over time. A problem has occurred particularly in that the characteristics deteriorate rapidly when ultraviolet rays are transmitted.
A communication optical fiber with a reduced transmission loss has been proposed for example in Japanese patent appln. publication No. 7762/1985, Japanese patent appln. publication No. 3020/1985 and Japanese patent appln. laid-open No. 62204/1981 but no energy transmission optical fiber for transmitting high-energy beams superior particularly in characteristics over time has been proposed.